Magnetic Wire Recorders Rule!

Avid sound recording enthusiast Jim Wood is in the process of constructing his own magnetic wire recorder from the ground up.

Before magnetic tape recorders appeared on the scene, their predecessors worked by rapidly pulling a wire over a recording/playback head. To be honest, I'd never even heard about these little beauties until a guy called Nick Gent told me the tale of how his grandfather had built his own wire recorder and made recordings of the family, including Nick's great grandparents and even his mother as a child.

Thus it was that, about a year ago as I pen these words, I wrote an article here on EE Times about magnetic wire recorders (click here to see that original article). Well, it's amazing how these tales keep on growing in the telling, because I was just copied on an email sent to Nick from a guy called Jim Wood who is in the process of constructing his own magnetic wire recorder from the ground up.

If there is a right man for the task, that man is Jim. I've since discovered that he and Mark Drake co-founded a company called Inovonics back in 1972. Jim's company is best known for producing high-quality broadcast audio processors, RDS/RBDS encoders, and AM/FM modulation monitors.

In his email to Nick, Jim explained that he was Googling "Wire Recorder" when he ran across my article on EE Times and read the story of Nick's grandfather. This made Jim think of an old advert from a 1949 issue of Wireless World magazine (shown below), which advertised parts for experimenters to construct their own wire recorders ("More thrilling than Radio -- More gripping than Television"), and which caused Jim to wonder if Nick's grandfather may have been inspired by something like this:

Nick responded that Wireless World was indeed quite likely to have been the inspiration for his grandfather, who was avid reader of hobby electronics magazines. Nick also noted that his grandfather probably paid a few visits to Park Radio -- the shop advertising the wire recorder parts -- because he lived only 20 miles from that establishment.

But we digress... It seems that Jim has been a passionate sound recording enthusiast for the better part of 60 years. When Jim was about 13, his dad bought him a used wire recorder, which became one of his most prized possessions. Even after Jim had graduated to tape later in the 1950s, the massive speaker in his wire recorder console cabinet was relegated to subwoofer duties for several years more.

Recently, Jim embarked on a project: to build a top-quality wire recorder employing present-day components and techniques. He is using a Webster Chicago mechanism, but is building all of the electronics from scratch. Below we see a shot of Jim's test bed, which he's using to develop the record and playback amplifiers and equalization circuits:

Jim says that, thus far, the major hurdle in the design has been accomplishing good low-frequency response. Due to the high wire speed (24 inches per second) and the small geometry of the record/reproduce head core, the initial response exhibited severe “head bumps” and egregious deviation from flat low-end response, as illustrated below:

Since then, Jim has changed the erase/bias circuitry from a linear amplifier to a power oscillator, which gives a slightly quieter recording. He's also implemented what he describes as "some fancy 'dip' filters" and performed a lot of SPICE simulations to achieve the required equalization, which is illustrated in the graph of the final overall frequency response shown below:

As an example, Jim attached a few seconds of an MP3 recording he made of a transfer from a vinyl LP to his wire recorder (click here to hear this recording). In his email to Nick and me, Jim modestly noted "It doesn’t sound bad at all." I don’t think Nick agrees with this assessment, because he immediately responded "The quality of that recording is stunning!" I have to admit that I'm with Nick on this one.

Jim says his job is demanding a lot of his time right now (I know that feeling), but when he gets back to this he plans to put it all together in a nice box of some sort and then "do some 'unique' location recording." Jim also says that when the whole thing’s finished, he plans on "doing a proper write-up of the project," which I hope he will share with us here on EE Times.

@Set Square: If you want to see a comercial version of the the science museum in London UK did have one on display...

I last visited the London Science Museum in 2010 when I was speaking at the Embedded System Conference (I also got my picture taken standing next to the "Dr Who" style Police Box outside of Earl's Court Tube Station, but that's another story) ... but I don't recall seeing this in the museum ... maybe it' sjust a case of not knowing what I was looking at...

@Set Square: If you are into Doctor Who, then if you ever find yourself in Bradford, yorkshire...

I've been into it ever since i saw the very first episode back in 1q963 when I was 6 years old!!! I'm from Sheffield, Yorkshire -- I occasionally get back to see my mom and little bro' -- the next time I'm over I will definately try to get over to Bradford to the National Media Museum (after which you can expect to see a follow-up blog) -- thanks for the suggestion!!!

I had heard of wire recorders several decades ago when I've watched some of the old WWII movies. When they wanted to record something (surreptitiously) they always used a "wire recorder" complete with a bobbin of "wire". One advantage of wire over tape would be the environmental "extremes" that the wire could survive versus a tape.

My favorite episode of Patrick MacGoohan's Secret Agent (aka Danger Man, in the UK) was the one in which the secret message was recorded on the twisted wire used to hang a picture in the spy's apartment. Can't do that with magnetic tape! Fortunately, MacGoohan was carrying a tiny wire playback machine so he could hear it. (I never leave home without mine).

@Tom: Fortunately, MacGoohan was carrying a tiny wire playback machine so he could hear it.

That reminds me of the old "Batman & Robin" film where batman is hanging from a rope ladder under the Bat Copter when a shark jumps out of the sea and attaches itself to Batman's leg ... and Batman shouts up to Robin "Pass me the Shark-Repellent Spray" -- and you see Robin in the cockpit reach for a rack containing four cans of sprak ... and sure enough one is marked "Shark Repellent" ... what are the odds?